Now Marty, the only dumb question is the one that is never asked. ANd since
PJM never asks any questions, he is the dumbest man alive.
However, on to your question:
Loosen the 3 screws a bit, and twist the disposal. SHould come right off.
And don't worry, you arn't going to break anything, so even if you end up
taking out every screw and smashing the old sink with a sledge - the old
disposal will still be good to go for your new sink.